Producing plural subterranean strata by in situ combustion and fluid drive



Dec. 29, 1964 c. A. STRATTON 3,163,215

paooucms PLURAL. SUBTERRANEAN STRA'I'A BY IN SITU COMBUSTION AND FLUIDDRIVE Filed Dec. 4. 1961 FIG.

INVENTOR. C.A. ST RATTON A T TORNEYS United States Patent "ice PRODUCINGPLURAL SUBTERRANEAN STRATA BY IN SITU COMBUSTION AND FLUID DRIVE CharlesA. Stratton, Bartlesviile, Okla, assignor to Phillips Petroleum Company,a corporation of Delaware Filed Dec. 4, 1961, Ser. No. 156,620 5(Ilaims. (Cl. 166-10) This invention relates to a process for theproduction of oil from two or more subterranean strata by in situcombustion and fluid drive.

In oil fields found in various locations, such as in the Monagas Fieldin Venezuela and the Danglemeyer Lease of North Texas, difl'erent oilzones having oil in diiferent viscosities are spaced apart byimpermeable barriers or strata. A less'viscous' oil zone may overlie amore viscous oil zone or vice versa. Also, a more viscous oil zone maylie between adjacent less viscous oil zones from which they areseparated by impermeable barriers. The less viscous oil zone may lieintermediate two or more viscous oil zones.

- Accordingly, it is an object of the invention to' provide an improvedprocess for producing two or more spacedapart, oil-bearing strataseparated by permeable layers. Another object is to provide a processfor producing such strata utilizing a combination of fluid drive and insitu combustion. A further object is to provide an arrangement ofapparatus in wells penetrating spaced-apart strata containing oil ofdifferent viscosities for producing said strata. Other objects of theinvention will become apparent upon consideration of the accompanyingdisclosure.

A broad aspect of the invention comprises producing hydrocarbons from anoil field including a less viscous oil-bearing stratum and a moreviscous oil-bearing stratum separated by an impermeable barrier andpenetrated by a pair of wells, which comprises, producing the lessviscous oil-bearing stratum by fluid drive between said Wells topartially deplete same, igniting the more viscous oil-bearing stratumaround one of said Wells to establish a combustion zone therein, drivingthe resulting combustion zone through the more viscous oil-bearingstratum toward the other well by feeding combustion-supporting gasthereto so as to produce a hot gaseous elfluent comprising hydrocarbonsand combustion gases in one of said wells, passing at least asubstantial portion of said hot eflluent directly from said one wellthrough the partially depleted, less viscous oil-bearing stratum to theother Well to produce additional hydrocarbons and recovering theproduced hydrocarbon from said other well.

The less viscous oil-bearing stratum may be produced by any type offluid drive, such as miscible fluid drive, water flooding, steam drive,or other gas or liquid drive not involving in situ combustion. The moreviscous oilbearing stratum is produced by either inverse or direct drivein situ combustion in a manner well known in the art. The gaseouseflluent from the in situ combustion drive is passed directly from theproduction Well through the partially depleted stratum containing theless viscous oil so as to produce additional oil therefrom and thehydrocarbons produced by both the in situ combustion step and the hotgas drive are recovered from one or more of the Wells in the strata.

The less viscous oil-bearing strata referred to herein includes anystratum which contains oil sufliciently fluid to be produced by fluidflood in reasonable quantity, such as to or percent of the oil in place.Oils of less than about 12 to 15 cps. are producible by fluid floodingin-sufi'icient quantity for operation of the process. The more viscousoil-bearing strata referred to herein are those containing heavy oil orsemisolid to solid hydrocarbon material not producible by fluid floodingbut 10- 3,163,215. Patented Dec. 29, 1964 cated in a straturn ofsuflicient permeability to permit moving a combustion zone therethroughby either direct or inverse injection of air. The less viscous oilsusually have an API'gravity of at least 20 or 25, while the more viscousoils have an API gravity of less than about 1 2.

A more complete understanding of the invention may be obtained byreference to the accompanying drawing of which FIGURE 1 is a fragmentarysection through a formation or' oil field showing one arrangement ofapparatus for elfecting the invention; and FIGURE 2 is a plan view of a5-spot well pattern for producing oil from an oil field in accordancewith the invention.

Referring to FIGURE 1, a more viscous'oil-bearing stratum 10 isseparated from a less viscous oil-bearing stratum 12 by an impermeablebarrier 14. These strata lie between an overburden 16 and a substratum18. All of these strata are penetrated by a pair of outer wells 20 andan intermediate well 22. Outer Wells 20 are provided with casing 24 andtubing string 26, While intermediate well 22 is provided with casing 28and tubing string 30. Lines 32 connect with casing 20 and With theannulus 34 in wells 20. Tubing strings 26 are extended toat least thelevel of impermeable barrier 14 and are surrounded by packers 36 whichpack ofl the annulus above and below impermeable stratum 14'. A packer38 may be provided around tubing string 30 and Well 22, if desired. Thecasing in each of the wells is provided with-perforations 40 which serveas means for passing fluids between the Wells and the strata as requiredin the process.

Referring to FIGURE 2, central well 22 is surrounded by four cornerwells 20. .Wells 20 in FIGURE 1 may represent diagonally opposite wells20 in FIGURE 2 and each may also represent one of the wells in twoparallel lines of wells spaced from a line of central wells 22 forin-line production.

Utilizing the arrangement of apparatus shown in the drawing, lessviscous oil-bearing stratum .12 is produced by fluid drive and bypumping in a conventional manner as by injecting fluid through tubing 30and forcingsame through stratum 12 intowells 20 from which production isrecovered by pumping or pressure lift through tubing 26. In thisoperation lines 32 must be kept closed so that injected fluid cannotpass through stratum 10 to annulus 34 of wells 20. After partialdepletion of stratum 12, stratum 10 is ignited adjacent well 22 by anysuitable means, and the resulting combustion zone is moved outwardlytoward wells 20 by injecting combustion-supporting, o -containing gas,such as. air, through lines 32 so as to move combustion zone 50 byinverse drive toward wells 20. The hot produced gases pass into well 22through perforations 40 leading into stratum 12 containing residual oil.The hot gases comprising hydrocarbons, combustion gas, and steam areforced through stratum 12 to wells 20 from which they are recovered,along with additional oil produced from stratum 12, through tube string26 in each of Wells 20.

It is feasible to produce a stratum containing highly viscous oiland oneof low permeability by in situ com- .bustion, particularly by inversedrive as illustrated in FIGURE 1 when the stratum is not amenable toproduction by fluid drive. The heating of the stratum by combustion of aportion ofthe oil raises the temperature thereof to a high level, suchas 800 or 900 to 1400 or 1500 F which renders the produced hydrocarbonssubstantially completely vaporous, thereby facilitating the drive ofthese vaporous hydrocarbons through the burned out, more permeablestratum behind the combustion zone. The hot vaporous effluent from thein situ combustion step provides an excellent gas fora gas drive throughthe partially depleted stratum containing less viscous oil.

In oil fields where stratum 10 contains oil of intermediate viscosityand sufiicient permeability is available in this stratum, the combustionzone may be driven through the stratum by direct drive. In this case,either combustion zones are established adjacent wells 20 and air isinjected through lines 32 or well 22 is equipped with a line 32 and apacker 36 around tubing 30 at the level of stratum 14 so that air can beinjected through line 32(connected with casing 28) so as to drivecombustionzone 50 by direct drive through stratum into wells from whichthe hot gas is forced into stratum 12 by omitting packers 36 in wells20. 'In this type of operation the arrangement of tubing and packers inwells 20 and well 22 is reversed so that produced gases are driven fromstratum 10 into wells 20 from which these gases pass directly intostratum 12 and are produced through tubing 30 which is extended below orat least to the level of stratum 14.

Where production is effected by means of three rows of in-line wells,thesame techniques may be applied. .It is to be understood that it isnot necessary to produce all of the effluent gas from the insitucombustion step in stratum 10 through stratum 12. A portion of thishot eflluent may be passed through a third-stratum (partially depleted)lying above the stratum 10, or below stratum 12. In the event the thirdstratum lies above stratum 10,

packer 38 must be placed above this third stratum. It is also feasibleto simultaneously produce more than one stratum, such as 10, by in situcombustion and force all of the produced gases through one or morepartially depleted strata in the same field.

Certainmodifications of the invention will become apparent to thoseskilled in the art and the illustrative details disclosed are not to beconstrued as imposing unnecessary limitations on the invention.

I claim: a

1. A process for producing hydrocarbons from an oil field including afirst permeable stratum containing liquid oil of relatively lowviscosity'and a second permeable stratum containing liquid oil ofrelatively high viscosity, said first and second strata being separatedby" an impermeable barrier and penetrated by a pair of wells, whichcomprises the steps of:

(1) substantially partially depleting the oil from said first stratum byfluid drive to recover oil therefrom and render same more permeable;

(2) igniting the liquid oil along the vertical extent of said secondstratum around one of said wells to establish a combustion zonecoextensive vertically with stratum;

(3) driving the combustion zone of step (2) thru the second stratum byfeeding combustion-supporting gas thereto thru the pores of thepermeable stratum so as to sweep a full cross section of the stratum andproduce a hotgaseous efliuent in one of said wells comprising asubstantial proportion of oil and combustion gases; I

(4) passing at least a substantial proportion of the hot elfluent ofstep (3) directly from said one well thru the partially depletedstratumof step (1) to the other 7 well to produce additional oil from last saidstratum;

and

(5) recovering oil produced from both strata fiom last as to move saidcombustion zoneby direct drive thru said second stratum.

' 4. The process of claim 1 wherein said fluid drive comprises amiscible fluid drive.

5. The process of claim 1 wherein said fluid drive comprises waterflood.

References Cited in the file of this patent UNITED STATES PATENTS2,584,605 Merriam et al Feb. 5, .1952 2,888,987 Parker June 2, 19592,954,218 Dew etal Sept. 27, 1960 3,034,580 Frey'et a1 May 15,19623,050,116 Crawford Aug. 21, .1962

OTHER REFERENCES Slobod, R. L.: A Review of Methods Used to Increase OilRecovery, Producers Monthly, February 1958, pp. 24-31.

1. A PROCESS FOR PRODUCING HYDROCARBONS FROM AN OIL FIELD INCLUDING AFIRST PERMEABLE STRATUM CONTAINING LIQUID OIL OF RELATIVELY LOW VICOSITYAND A SECOND PERMEABLE STRATUM CONTAINING LIQUID OIL OF RELATIVELY HIGHVISCOSITY, SAID FIRST AND SECOND STRATA BEING SEPARATED BY ANIMPERMEABLE BARRIER AND PENETRATED BY A PAIR OF WELLS, WHICH COMPRISESTHE STEPS OF: (1) SUBSTANTIALLY PARTIALLY DEPLETING THE OIL FROM SAIDFIRST STRATUM BY FLUID DRIVE TO RECOVER OIL THEREFROM AND RENDER SAMEMORE PERMEABLE; (2) IGNITING THE LIQUID OIL ALONG THE VERTICAL EXTENT OFSAID SECOND STRATUM AROUND ONE OF SAID WELLS TO ESTABLISH A COMBUSTIONZONE COEXTENSIVE VERTICALLY WITH STRATUM; (3) DRIVING THE COMBUSTIONZONE OF STEP (2) THRU THE SECOND STRATUM BY FEEDINGCOMBUSTION-SUPPORTING GAS THERETO THRU THE PORES OF THE PERMEABLESTRATUM SO AS TO SWEEP A FULL CROSS SECTION OF THE STRATUM AND PRODUCE AHOT GASEOUS EFFLUENT IN ONE OF SAID WELLS COMPRISING A SUBSTANTIALPROPORTION OF OIL AND COMBUSTION GASES; (4) PASSING AT LEAST ASUBSTANTIAL PROPORTION OF THE HOT EFFLUENT OF STEP (3) DIRECTLY FROMSAID ONE WELL THRU THE PARTIALLY DEPLETED STRATUM OF STEP (1) TO THEOTHER WELL TO PRODUCE ADDITIONAL OIL FROM LAST SAID STRATUM; AND (5)RECOVERING OIL PRODUCED FROM BOTH STRATA FROM LAST SAID OTHER WELL.